Electric power busway used within industrial power distribution systems generally consist of a plurality of rectangular copper or aluminum bars closely spaced and separated by means of an electrically insulative coating. Every two feet or so, the bars are shaped to provide a spaced gap between the individual bars and the bottom edge of each of the bars is abraded to remove the insulative material and expose a contact region on both flat sides of the bar. This exposed contact is then tin or silver-plated to provide an electric contact blade for connection with a power take-off assembly which includes a corresponding plurality of blade receiver stabs which mate with the blade portions of the shaped bars. The air gaps between the shaped bars provide sufficient electrical insulative spacing to prevent arcing between the different phases of a multi-phase power system wherein each bar carries one-phase of the system current. The so-called "expanded connector region" containing the shaped bars effectively provide electrical access to the busway by means of the contact blades. When a four-bus power distribution system is employed, the added length for each expanded connector region corresponds to an increase of approximately six percent for each bar. For the four-bus power distribution system, this represents an equivalent six percent increase in the weight of conductor material over an equivalent linear distance spanned by the closely spaced bars within the remaining extent of the bus system. For the long lengths of busway required in most industrial operations, the amount of extra conductor material required to provide sufficient expanded connector regions is substantial.
U.S. patent application Ser. No. 122,863 filed Nov. 19, 1987 entitled "Thermally Efficient Power Busway Housing" describes a lightweight electrical power bus assembly that includes power bus conductors bolted to the power bus housing. To expand these bus bars to provide for connection with thepower take-off assembly would create thermal loads to the system to substantially reduce the overall thermal efficiency. This Patent Application is incorporated herein for purposes of reference and should be reviewed for its teachings of the use of thermally conductive and electrically insulative coatings.
U.S. patent application Ser. No. 107,320 filed Oct. 13, 1987 entitled "Power Distribution Busway System" teaches the use of an expanded integrally formed contact blade on each of the bus bars in the power take-off region of the system to allow for connection with the power take-off assembly without expanding the respective bus bars. This Application is also incorporated herein for purposes of reference. The use of integrally formed contact blades, however, requires expensive forming equipment that must be incorporated within the bus bar manufacturing operation. The present invention proves a simpler and more cost efficient method of providing extended contact blades.
U.S. Pat. No. 4,394,532 and Japanese Patent 40590 both describe the attachment of linear contact blades to miniaturized bus bars used within electronic computers for electrical connection with the individual bus bars. The attachment of linear contact blades to industrial power distribution systems carrying currents in excess of hundreds of amperes, however, has not heretofore proved commercially feasible.
One purpose of the instant invention therefore, is to provide a power bus system which allows interconnection with a plurality of power take-off assemblies without increasing the amount of conductor material at each individual power take-off position and without having to expand a part of the individual power buses.